President Obama put a small amount of political capital into Tuesday's primary races, but the more revealing in the end were all the things he didn't do.
In Pennsylvania, Obama steered clear of Sen. Arlen Specter's re-election bid -- although he endorsed and raised money for the former Republican. A rumored, last-minute campaign event for Specter by Vice President Biden never materialized.
Obama endorsed Specter but kept him and Arkanas Democratic Sen. Blanche Lincoln at arm's length in their primary battles. The treatment underscores how the president's support can cut both ways in his own party, and White House disinterest in bearing blame when Democrats lose.
"We have supported incumbent Democratic senators and we've done a lot on behalf of each campaign," White House press secretary Robert Gibbs said of Lincoln and Specter.
But there are limits to how Obama's support can be helpful. In Pennsylvania, the president's job approval rating is 50 percent, according to Rasmussen Reports. In Arkansas it's 35 percent.
Lincoln ran as an independent-minded Democrat who fought the administration on cap and trade legislation and health care reform, and only supported the latter after a government-run insurance program was dropped.
Her opponent, Attorney General Bill Halter, backed by organized labor, promised to push Obama toward more liberal policies on health care, trade and other issues.
In Pennsylvania, Rep. Joe Sestak fashioned himself as the true Democrat in the race, running a series of withering campaign ads over Specter's 2009 defection from the Republican Party.
For Specter, a high-profile and last-minute push from Obama could have helped in Philadephia, but hurt in the bedrock Democratic precincts outside the city where the race was more closely contested.
Obama put in one appearance for Specter, appearing at a rally in Philadelphia last year. Biden did an event for Specter, his old colleague from the Senate, in April. But speculation that Biden would do so again in conjunction with a Philadelphia graduation speech he delivered Monday didn't materialize.
Obama made zero appearances for the special election to replace the late Rep. John Murtha in Pennsylvania, although the longtime Democratic seat was in danger of flipping to Republican Tim Burns. Instead, former President Clinton campaigned for Democrat Mark Critz.
The White House has tried to downplay speculation about how Tuesday's results might reflect on Obama. He is a sought-after and prodigious fundraiser, but his track record of campaigning for Democratic candidates has not been a winner.
Last year, Obama campaigned for Democrats in statewide races in New Jersey, Virginia and Massachusetts. All three lost.
Gibbs said Obama was following the various Tuesday primary races, but "not that closely."
In much the same way incumbents Lincoln and Specter were chary of Obama's political embrace, the White House doesn't want Obama too frequently characterized as a vote killer for Democratic candidates.
That portends some tough luck for the Democrat who emerges from the Senate primary race in Kentucky to face Republican primary winner Rand Paul in November. Obama's statewide approval rating in Kentucky is 41 percent, according to Rasmussen.