As Democratic primary voters in Arkansas and Pennsylvania head to the polls Tuesday to render a verdict on Sens. Blanche Lincoln and Arlen Specter, all eyes in Washington, D.C., are fixated in their direction in search of clues for what lies ahead in November.

Lincoln, pitted against Arkansas Lt. Gov. Bill Halter, is expected to win her contest, with the only question being whether she can avoid a June 8 runoff. Specter, meanwhile, is in a real dogfight against Rep. Joe Sestak in Pennsylvania’s Democratic Senate primary, with public polling showing that race tied.

“I believe that Specter will possibly pull it off, but that Sestak probably wins,” a Capitol Hill Democratic leadership aide said. “I think Blanche is going to win, which is astounding considering where we were a few months ago. … But I think it still likely goes to a runoff.”

A second Democratic aide, a senior adviser in the Senate who believes Lincoln and Specter would prevail, said that the Conference would closely monitor Tuesday’s events. This aide said Democratic Senators are unlikely to read too much into these contests, regardless of their outcome, given what is perceived as the special circumstances of each.

Specter was a Republican for 40 years before switching parties in April 2009. He has spent the year getting to know Pennsylvania Democrats, and Sen. Bob Casey (D-Pa.), whose family has deep roots in Keystone State politics, has given the former Republican rave reviews. But in the waning days of the primary, Specter has exhibited the perils of the switch, occasionally thanking “Republicans” for their support in front of Democratic audiences.

Lincoln became a target of labor unions and liberal activists after resisting the public insurance option proposal during the contentious yearlong debate over health care reform, even though she provided a crucial vote that enabled President Barack Obama to sign the bill into law. Lincoln remains highly vulnerable in the general election, but her trouble in the primary is attributed more to national, out-of-state groups, as opposed to unhappy Arkansas Democrats.

“Other than the fact that they’re both incumbents, there’s nothing similar about each of these races, so it’s hard to extrapolate too much from either,” the senior Democratic Senate aide said. “The Caucus is confident that we’ll win both. Not that it’s going to be pretty, but that we’ll win.”

In the Pennsylvania race, the RealClearPolitics.com average of all public opinion polls taken May 3 through Sunday gave Sestak an edge over Specter of 44 percent to 41 percent. The last few days of the campaign have seen a battle for voter turnout, with Sestak’s team using phone banks to log 30,000 calls and Specter’s people canvassing the state to knock on 34,500 doors. Both candidates’ political bases are in Philadelphia, a Democratic stronghold, and the surrounding suburbs.

Senate Banking Chairman Chris Dodd (D-Conn.), who chose retirement over an uphill battle for re-election, acknowledged that this year’s midterm elections have the aspects of a national race, and he said his fellow Democrats would be following the results of Tuesday’s primaries with interest. However, he stopped short of saying the fate of Lincoln and Specter would influence their votes on major legislation moving forward.

“Oh sure they’re paying attention. It would be silly to say otherwise,” Dodd said Monday. “But I can’t say how much.”

National Republican Senatorial Committee Chairman John Cornyn (Texas) said the winner of Tuesday’s Democratic primaries isn’t particularly important, belying the confidence the GOP has heading into the last five and a half months of the midterm campaign.

“I feel confident that we’ll pick up both of those seats,” Cornyn said.

One sector of the Washington community that is watching the Lincoln and Specter primaries with keen interest is K Street. The outcome of each contest could determine the flow of campaign cash to Democratic and Republican candidates and — counter to what Dodd believes — could affect votes on major legislation.

Should Lincoln and Specter both lose, Republican candidates — particularly the GOP nominees in Arkansas and Pennsylvania — could see a spike in campaign contributions from K Street, including from individual donors and political action committees, according to one lobbyist. This individual also believes that Tuesday’s elections could influence the final form of Dodd’s financial regulatory reform package, particularly Lincoln’s proposal to overhaul the regulation of derivatives.

“I think every single person on K Street is watching this, and I say that without any hesitation,” the lobbyist said.

Meanwhile, organized labor has none of K Street’s hesitation, with labor groups playing a starring role in the Arkansas race and heavily involving themselves in Pennsylvania’s.

The Arkansas race has become as much of a battle between the moderate Lincoln and the labor groups who targeted her for defeat this cycle as it is a race between Halter and the Senator. While spending reports continue to be filed, some estimates put the total amount spent by labor groups on the Arkansas race at $7 million, with $4 million of that going to television advertising.

Labor leaders have crowed that that investment has already paid dividends by getting Lincoln to move left on issues like regulatory reform. It’s also put other Members on notice that the labor movement isn’t afraid to play anywhere, even in a state that’s on the lower end of labor representation.

But with Halter having moved very little in polling since his entrance into the contest on March 1, it’s hard to imagine that labor groups will get the final payoff of ousting Lincoln.

Some labor insiders are starting to wonder whether it’s been worth the investment. Did labor go too far out on a limb with Halter and were the potential rewards worth it, especially when labor will have several key supporters in tough races this fall, are the questions some labor activists are posing.

“We’re going to have a hell of a challenge in Illinois, we clearly have a hell of a challenge in Nevada, we’ve got opportunities in Ohio and Missouri. To be eating your own in a state like Arkansas for the purpose of saying we showed her smacks of a lack of good judgment,” said one political director from a group affiliated with the AFL-CIO.

Veteran labor strategist Steve Rosenthal said Monday that the movement has made an important statement by backing Halter.

“How anybody could possibly define whatever the outcome is as a loss is beyond me,” he said. “If it is a runoff and Halter eventually wins the thing, then Hallelujah. But the bottom line is the message to elected officials has already been delivered.”