Rep. Joe Courtney (D-Conn.) announced Monday morning that he will not run for the Senate in 2012, a decision that further solidifies the Democratic field in the race to replace retiring Sen. Joe Lieberman (I).

“I am truly grateful for the tremendous encouragement and enthusiastic support I have received from leaders across Connecticut as I have considered this question,” Courtney said in a statement. “I look forward to working with all of those who reached out to create a strong future for our state. After careful deliberation, however, I have decided to focus on my work as a Congressman and will decline to enter the race for the Democratic nomination for the U.S. Senate.”

Among his reasons, Courtney cited efforts by House Republicans to endorse funding cuts for Connecticut’s 2nd district during last week’s budget debate.

“House Republicans last week pushed through a measure to slash support for our firefighters, gut funding that helps homeless veterans, and ended critical infrastructure investment and the jobs that go with it,” he said. “Their efforts highlight what is at stake for this district, and why it is critical that eastern Connecticut continue to have a strong voice defending its priorities over the next two years.”

The decision is good news for Democratic efforts to hold Courtney’s House seat in 2012. It’s the largest district geographically in the state and one that was held by a Republican (former Rep. Rob Simmons) as recently as 2006. Courtney’s decision also helps clarify the field for the two Democrats already vying for Lieberman’s seat

Last week, Edward Kennedy Jr., son of the late Senator and an investment banker, ruled out a run. Combined with Courtney’s announcement, that leaves just two announced Democrats.

Longtime Secretary of State Susan Bysiewicz (D) jumped into the race in late January. She enjoys strong name recognition statewide and released internal polling last month suggesting that she held a strong lead over potential challengers, including Rep. Christopher Murphy (D).

Murphy, long thought to be a rising star on Capitol Hill, announced his candidacy the day after Lieberman made clear his intention not to run again. He also released his own polling numbers that showed he has an advantage.

While Kennedy and Courtney are out, there’s at least one more Democrat to watch: Frank Borges (D), a centrist with strong connections in the investment community, who has been courting key Connecticut Democrats in recent weeks.

Roll Call Politics rates the Senate race Leans Democratic, a rating that likely wouldn’t change regardless of the Republican field because of the Nutmeg State’s Democratic leaning electorate. Democrats currently occupy all five Congressional districts and virtually every other statewide office.

Republicans to watch include Simmons, who fell by a razor-thin margin to Courtney in 2006, and former Senate candidate Linda McMahon. She has the wealth and name recognition to dramatically change the tone of the 2012 contest, but she lost by 10 points to Sen. Richard Blumenthal last November.