If you’re wearing a blue uniform but your game is in a stadium where most of the crowd usually roots for the reds, try accessorizing with as much purple as possible.

That bit of fashion advice is one cheeky way of describing the politically pragmatic behavior of most, but not all, of the 10 Democratic senators hoping to hold their seats this fall in states that went for President Donald J. Trump.

Tomorrow’s voting in Texas, the first congressional primaries of 2018, is something of an official starting gun for the midterm election. Attention will focus first on the Democrats’ drive to take back the House, but a real return to divided government requires the party to win its tough but not impossible struggle for the Senate — and that starts with each one of their politically vulnerable incumbents winning re-election.

Trends beyond their control, starting with the national mood and Trump’s sagging approval numbers, in many cases will not prove as important to these senators as their individualized electoral salesmanship back home. And voting records can play a vital role in establishing a lawmaker’s personal political brand.

These days, when tribal partisan loyalty defines life for the vast majority in Congress, a lawmaker whose voting record stands out for going against the grain is almost always a lawmaker staring political death in the face. But for a senator from one party in a state where the other party is dominant, the simplest way to survive is to come off as politically independent.

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“Reach across the aisle,” “seek common ground” and “put the people I represent ahead of my party” may be the aphorisms of choice. Yet for Democratic senators running in Republican states, nothing expresses a commitment to bipartisan centrism as tangibly as voting with Trump, and against Minority Leader Charles E. Schumer, as often as they can live with.

It’s hardly surprising, then, that the four Democrats in the toughest races at the moment — eight months from Election Day, each is no better than an even-money bet for re-election — are also the four who backed Trump most often during the first year of his presidency, and at the same time also bucked party leadership most frequently.

West Virginia’s Joe Manchin III, who’s seeking his second full term in Trump’s best state from 2016 (he took 69 percent of the vote), voted with the president 71 percent of the time when his wishes were clear in advance. Manchin also bucked his caucus on 36 percent of the roll calls where most senators from one party voted differently from most senators on the other side.

Heidi Heitkamp of North Dakota, which Trump carried by 36 points, voted the president’s way two-thirds of the time and went against the partisan grain 30 percent of the time.

Joe Donnelly of Indiana and Claire McCaskill of Missouri (Trump won both states by 19 points) took the president’s side on roughly three out of every five votes in a year when the average Democrat did so on three out of every eight. Donnelly bucked the majority of his colleagues four times more than the typical Democrat (26 percent versus a caucus average 6 percent) and McCaskill did likewise three times as often.

Manchin, Heitkamp and Donnelly, for notable example, were the only Democrats who voted to confirm Neil Gorsuch for the Supreme Court.

And their apostasies were not unique to their first year “in cycle,” the shorthand for a senator within two years of standing for re-election. While McCaskill, who will likely be seeking her third term against 38-year-old state Attorney General Josh Hawley, moved somewhat rightward between 2016 and 2017, the others also opposed President Barack Obama’s final-year agenda — and bucked their partisan colleagues — more often than any other Democrat.

All these numbers come from the latest iteration of the presidential support and party unity calculations our colleagues at CQ have been conducting annually since the Eisenhower administration.

The next tier

Measuring centrism by the numbers, there’s a significant drop-off between the four in toss-up contests and their colleagues in serious, if slightly less dire, political trouble.

Montana’s Jon Tester and Florida’s Bill Nelson stood with Trump just half the time, while Wisconsin’s Tammy Baldwin, the third Democrat who at the moment stands as only the slightest favorite, did so on 36 percent of the votes.

That’s in line with the average for a Senate Democrat last year, a relatively high number mainly because senators cast dozens of votes to confirm the president’s noncontroversial nominees. The two Trump-state incumbents in races currently seen as just leaning in favor of re-election, Sherrod Brown of Ohio and Bob Casey in Pennsylvania, had scores in line with the caucus average. So did the only senator among the 10 who now looks like a safe bet to win in November, Debbie Stabenow of Michigan.

While those voting records cannot properly be cited as evidence that those senators in the second tier are reliable bipartisan centrists, neither can they be fairly used to claim they are reflexive Trump antagonists — a label that wouldn’t do any particular good in states that might generally be characterized as purple. (Florida, Ohio, Pennsylvania, Wisconsin and Michigan all went for Obama twice before flipping to Trump last time, in almost each case by a tiny margin.)

But for two of them, the vote studies reveal a clear tack to the right: Tied for the fourth-highest Obama support score just a year earlier were Nelson, who may be preparing for an intense campaign against Gov. Rick Scott, and Casey, who has a clear if not dispositive edge over Rep. Lou Barletta.

Since the party now controls 49 seats, taking over the Senate requires a net pickup of two more, and that’s nearly impossible without a successful defense by all the endangered Democrats.

Loyal opponents

Republican House members figure in most of the Trump-state races where an incumbent Democrat is running. And while there are broad ranges of fealty to the Trump agenda and the Democratic leadership among the incumbent senators, all of their would-be challengers from Congress can fairly be described as loyalists to both the president and the House GOP party line.

Barletta was among an astonishing 77 members, or about one-third of the Republican Conference, who voted Trump’s way on all three-dozen of the House votes last year where he pushed for a particular outcome. So was Kevin Cramer, Heitkamp’s opponent in North Dakota.

Clocking a 97 percent support score was West Virginia’s Evan Jenkins, who has to get past a primary against state Attorney General Patrick Morrisey in order to challenge Manchin. The House GOP average was 95 percent, and just a hair below that were Ohio’s James B. Renacci, Brown’s challenger, and both Indiana congressmen vying to take on Donnelly, Luke Messer and Todd Rokita.

Those GOP members also had party unity scores within 3 points of the 95 percent House average.

In addition to a pair of open seats (Arizona and Tennessee), the Democrats’ current game plan for winning the Senate includes a well-financed assault on just a single incumbent Republican: Dean Heller of Nevada, which Hillary Clinton carried by a modest 2 points two years ago.

It is going to be a campaign between two lawmakers with voting records that count as “moderate” in today’s polarized climate.

Heller voted against Trump just five out of a possible 117 times last year, but that was enough for fourth place on the roster of Senate GOP presidential dissenters. And his challenger, House freshman Jacky Rosen, voted with Trump just 10 out of a possible 36 times, which was often enough to rank eighth in presidential support among the 193 House Democrats.