Bill Clinton today endorsed Dan Roberti in his bid for the Democratic nomination in Connecticut’s 5th district.

The endorsement comes just one day before the primary, and it’s unclear how effective it will be in boosting Roberti over former state Rep. Elizabeth Esty and state Speaker Chris Donovan.

“Whether running a homeless shelter, organizing rebuilding efforts after Hurricane Katrina, or helping veterans find jobs, Dan has demonstrated a deep commitment to public service,” Clinton said in a statement. “He’s always working to make a difference for other people, and he’s good at it.”

Clinton has been highly active this cycle, endorsing many candidates who have previously support either him or his wife, Secretary of State Hillary Rodham Clinton.

A quick scan of Federal Election Commission records shows that Roberti was an early 2007 donor to the presidential campaigns of both Hillary Rodham Clinton and now-President Barack Obama. Sources in the Esty and Donovan campaigns dismiss Clinton’s backing of Roberti, saying it has to do with the former president’s ties to Roberti’s father, Vincent Roberti.

According to FEC records, a “Vincent Roberti” has spent the last decade consistently donating to Hillary Rodham Clinton’s campaigns, but he also donated to then-New Mexico Gov. Bill Richardson’s 2008 presidential campaign. There are two Vincent Robertis in the family and records did not differentiate between the senior or junior.

In most, but not all, cases, Clinton has been an effective surrogate for House candidates in Democratic primaries. Candidates brag about his endorsement in television advertising. Clinton also has appeared at campaign events and has performed robocalls.

Political strategist James Carville, a former Clinton advisor, also is a prominent Roberti-backer.

In other news, Roberti scaled back his campaign over the weekend, because of the passing of his mother.

This is an open-seat race because Rep. Christopher Murphy (D) is running for Senate. Roll Call rates this race as Leans Democratic.