Rep. Rodney Alexander’s (La.) shocking party-switch Friday evening returned House Republicans to a 12-seat majority, nullifying Democratic gains made in two special elections earlier this year.

His decision, which came as a surprise to observers on both sides of the aisle and may involve a high-profile committee assignment, instantly evoked lavish praise from his new Republican brethren.

“I welcome him to the GOP and I look forward to working with Rodney,” said National Republican Congressional Committee Chairman Tom Reynolds (N.Y.).

Rep. David Vitter (R-La.), who is running for the state’s open Senate seat, endorsed Alexander in the 5th district race, adding: “I am excited to welcome Rodney Alexander to the Republican party.”

Alexander will begin caucusing with Republicans when Congress reconvenes after Labor Day. He will be in Washington on Tuesday to meet with GOP leaders.

House Republicans now have 229 House seats to 206 seats for Democrats (including one Independent).

Democrats were irate about their change of momentum.

Rep. Robert Matsui (Calif.), the chairman of the Democratic Congressional Campaign Committee, described Alexander as a “cowardly turncoat.”

Louisiana Sen. Mary Landrieu (D) sounded a similar note: “Nobody likes a coward, least of all the voters of Louisiana.”

It seems likely that Democrats will have to wait at least two years before they attempt to exact their revenge on Alexander, although officials at the DCCC said they were exploring a variety of potential options at press time.

After initially filing as a Democrat on Aug. 4, Alexander changed his mind just 30 minutes before filing closed on Friday, essentially ensuring that no serious Democrat would have time to make the race.

Former state Rep. Jock Scott qualified as a Republican while the lone Democrat now in the race is Zelma “Tisa” Blakes, a homemaker from Monroe.

Alexander told a local Louisiana newspaper that Blakes’ decision to run, which came on Thursday, ensured he would not have the full backing of the party in the fall.

Under Louisiana law, all filed candidates run in an open primary on Nov. 2. If no one receives 50 percent of the vote, the two top finishers, regardless of party affiliation, advance to a Dec. 4 runoff.

His explanation rings slightly hollow, however, as Alexander was all but assured of winning a second term as a Democrat since national Republicans failed in their efforts to recruit former 5th district Rep. John Cooksey (R) into the contest.

In a poll released by his campaign in early July, Alexander led Scott by a whopping 66 percent. Scott is expected to remain in the race.

The 5th district is located in northeastern Louisiana and tilts heavily toward Republicans. In the 2000 presidential race, George W. Bush carried it with 57 percent, his second best showing in the state’s seven districts. Alexander won it by just 974 votes in 2002.

By filing for re-election as a Republican, Alexander seemingly closed the book on a six-month odyssey that dominated his first term in office.

In March, Alexander was heavily courted to cross the aisle before ultimately deciding to stay put. Many Democratic insiders had been convinced he had decided to abandon them before Alexander put out a statement affirming his commitment to remain in the party.

Although rumors flew fast and furious about what Alexander was offered by Republicans in exchange for a party switch, knowledgeable Democratic sources said the prime motivator for him at that time was a concern that if elected to a second term, the party leadership would be less driven to help him secure dollars for his district.

According to published reports, Alexander has been offered a seat on the powerful Appropriations Committee although Republican sources could not confirm that enticement.

Alexander’s switch is the second of the year.

In January, Rep. Ralph Hall (Texas) became a GOPer following a Republican-led redistricting in the Lone Star State.

Those two switches canceled out Democratic gains stemming from victories in special elections earlier in the year.

Rep. Ben Chandler (D) won Kentucky’s 6th district in February while Rep. Stephanie Herseth (D) won the South Dakota at-large seat on June 1.

It marked the first time in more than three decades that Democrats had picked up two GOP-held seats in special elections in a single cycle.