On a day when two Democratic Senators were fighting for their political lives, President Barack Obama was donning a hard hat and taking a tour of an Ohio manufacturing plant.

But Senate Democrats say the fact that Obama wasn’t out front and center for their colleagues at their time of need doesn’t mean that he isn’t doing all he can to help — even if it means staying out of sight.

Obama endorsed Sens. Blanche Lincoln (Ark.) and Arlen Specter (Pa.) months in advance of Tuesday’s primary elections.

Since then, both faced increasingly daunting poll numbers, and the president took different tacks to aiding their campaigns. That is, until recently, when Obama began steering clear of both of them.

“That’s a decision based on the value it brings” to each individual candidate, Sen. Frank Lautenberg (D-N.J.) said.

“I think he’s done what he can,” Sen. Dianne Feinstein (D-Calif.) added. “I think he’s done a great job.”

Several Senate Democrats agreed that the president played a key role in helping Lincoln and Specter wage difficult campaigns. They attributed Obama’s decision to stop being as involved as the primaries neared, at least publicly, to part of a larger strategy that’s based on what best helps the candidate.

“I know that he helped Blanche. I know he’s been positive about Specter,” Sen. Amy Klobuchar (D-Minn.) said.

“I never second-guess what the president decides when getting involved in political campaigns,” Sen. Ben Nelson (D-Neb.) said.

The decision by the president to play a less prominent role in Tuesday’s races “is something that’s communicated between the White House and the campaigns,” Sen. Benjamin Cardin (D-Md.) said. He said Obama “closely supported” Lincoln and Specter throughout their bids, and the real issue is “how it’s been translated.”

Obama had made clear overtures to help other Democratic Senators in the past several months who are facing tough November races. He has headlined fundraisers for Sens. Barbara Boxer (Calif.) and Michael Bennet (Colo.) and, most notably, Majority Leader Harry Reid (Nev.).

A senior Senate Democratic aide contrasted how differently Obama had to approach Lincoln’s and Specter’s campaigns based on each of their state’s demographics: He avoided appearances with Lincoln — who represents a conservative state — for fear that he would be a political liability, whereas with Specter, he and Vice President Joseph Biden personally campaigned in his home state and hosted fundraisers.

Lincoln “probably would have told Bill Clinton to stay away, but he used to live there. Her whole strategy was to stay as far away from ‘Washington insiders’ as possible,” the aide said.

Another Democratic leadership aide agreed that Obama’s absence from Lincoln’s campaign was a strategic decision meant to help her. “If they wanted him there, I think he would be there,” the aide said.

By contrast, Specter benefited from a spate of robocalls and television advertisements cut by Obama. And despite seeming contradictory, it was “the right call” for Obama to avoid stumping for Specter on Tuesday since Election Day rallies often lead to minimal results and drain campaign resources, the senior aide said.

“I think he’s been a very strong and effective supporter” of Specter, fellow Pennsylvania Democratic Sen. Bob Casey said.

Casey said he barely caught any television last weekend and still saw an advertisement air five times that showed Obama endorsing Specter. The fact that Obama hasn’t been making appearances with the Republican-turned-Democrat shouldn’t overshadow the “substantial” push behind the scenes from the White House through “all kinds of other communications, like e-mails,” he said.

But Obama was already seen as distancing himself from Specter in the weeks leading up to Tuesday’s vote, with no visits to Pennsylvania even as Specter was facing an increasingly tight race against liberal Rep. Joe Sestak. The lack of action spurred talk that Obama may be seeking to avoid the embarrassment of a last-minute push for a candidate who goes on to lose — a scenario that played out in January in the Massachusetts Senate race to replace the late Sen. Edward Kennedy (D). In that case, Obama dashed up to do a last-minute event for Democratic Attorney General Martha Coakley, who went on to lose to now-Sen. Scott Brown (R).

White House Press Secretary Robert Gibbs dodged questions Monday about whether the outcome of Tuesday’s races will have much bearing on the president’s political standing and agenda.

“I’m happy to talk about the results when they happen. Obviously, I don’t think it’s breaking news to say that this has been, based on the election results that we do know, it’s been a tough year for incumbents,” Gibbs said.