Moderate Senate Democrats — many of them on the ballot in 2018 — came together with a unified message Tuesday morning, just before President Donald Trump arrived at the Capitol to meet with the Republican Conference.

Sen. Tim Kaine was perhaps the most direct. The Virginia Democrat said at the news conference that the GOP should make a run at a bipartisan product before bringing to the floor a tax reconciliation bill that would only require a simple majority to pass.

“Why not test us? Why not test us?” Kaine said. “You’ve got a reconciliation bill that you can pull up for a vote at any time, but why not test what we’re saying?”

Republicans view the Democrats’ opposition as a political winner for them, especially in states such as Missouri, which Trump won by 19 points last fall, and where he is heading for rally Wednesday.

But Democrats from those states, including Missouri’s own Claire McCaskill, view the GOP tax plan as toxic.

“He just hasn’t lived up to his promise on this bill. He said it wasn’t going to help him. This bill helps him immensely, tens of millions of dollars,” McCaskill said of the president. 

“He said it wasn’t going to be for rich people. It is for rich people,” she added. “He said it was going to simplify the tax code. Joint Tax Committee says it’s going to add another 10,000 pages to the tax code. That is not simplification.”

Watch: Protesters Chant ‘Kill the Bill’ as Tax Overhaul Advances From Senate Committee

Senior administration officials made clear Tuesday that Trump’s message in Missouri would feature criticism of McCaskill.

He is expected to call out the Democrat over her opposition to the Senate tax plan, senior administration officials said. 

It won’t be the first time McCaskill has come under fire from Trump on her home turf. In late August, Trump told Missourians at a rally in Springfield, “You have to vote her out of office” if she won’t support a tax overhaul.  

But McCaskill has been pushing her argument that the tax bill will harm Missouri residents. Her campaign sent out a fundraising email Monday that referenced a video of McCaskill confronting Senate Finance Chairman Orrin G. Hatch about the bill’s effect on Medicaid.

“The video of Claire calling the GOP out is funny (and going viral!), but this tax bill will have life-or-death consequences,” the email read. “If you believe in real, fact-based governing that helps the American people, donate right away.”

Political consequences?

Trump has already threatened retribution against some of the Democrats present at Tuesday’s news conference who oppose the current plan. 

Sen. Joe Donnelly of Indiana, for instance, noted that he traveled to his home state for tax events with both Trump and Vice President Mike Pence, the former Hoosier State governor.

“If Sen. Donnelly doesn’t approve it, because you know he’s on the other side, we will come here. We will campaign against him like you wouldn’t believe,” Trump said at a Sept. 27 event in Indianapolis. “I think we’ll have numerous Democrats come across because it’s the right thing to do.”

Thus far, Trump’s powers of persuasion have proved to be lacking, even with senators from states where he scored lopsided electoral victories over Democrat Hillary Clinton in 2016, such as Indiana, Missouri, North Dakota and West Virginia. 

Whether Trump can make life difficult for Democratic senators who oppose the GOP plan remains to be seen. And with the 2018 midterms less than a year away, it’s too early to tell what the top issue on voters’ minds will be when they head to the polls.

Republicans claim they need to pass a tax overhaul package to prove they should maintain control of both chambers. With that in mind, GOP groups have been spending substantial time and money boosting Republican support, with some also pressuring the red-state Democrats.

Targets on their backs

The pro-Trump group America First Policies launched five-day broadcast and cable ads Monday targeting Democratic Sens. Joe Manchin III of West Virginia, Heidi Heitkamp of North Dakota and Tammy Baldwin of Wisconsin, as well as a handful of Republicans who were on the fence.

The ads, first reported by The Wall Street Journal, cost the group $500,000. 

A GOP strategist said Democratic opposition to a tax bill will further boost one of the Republicans’ key messages against these vulnerable Senate Democrats: that they are closet liberals.

“One of the big hits that we have on these Democratic senators is that while they pretend to be a moderate on the big issues, they always come down on the Democratic side,” the strategist said. “And this is going to give us another high-profile thing to point to.”

But Democrats are confident they can fend off those attacks, thanks to these senators’ personal brands in their states, the unpopularity of the GOP proposals, and the fact that midterm elections rarely favor the party in power.

“If you’re a Democrat, responding to that is easy,” one Democratic strategist said. “‘I’m doing what I think is best for my state.’”

Republicans point out that Trump is still popular in a number of the states he won last fall by wide margins. There are 10 Democrats running for re-election next year in Trump states, including five in states he won by double digits.

If Wednesday’s visit to Missouri is any indication, he is willing and able to hit those red-state Democrats. McCaskill’s potential GOP opponent, state Attorney General Josh Hawley, will attend Trump’s event.

The Democratic strategist said emphasizing the bill’s negative effects on their constituents is a smart move for Democrats such as McCaskill, even in states where Trump remains popular.

“She can campaign saying, ‘I’m going to serve as a check,’ saying one-party control is not working,” the strategist said, adding, “‘I’m fighting for you, not Donald Trump.’”

Lindsey McPherson contributed to this report.