Republican leaders closed ranks Wednesday behind Delaware’s newly minted Senate nominee, Christine O’Donnell, moving to quell a budding feud over her candidacy between the Washington, D.C., GOP establishment and tea party activists nationwide.

Fearing that their refusal to assist O’Donnell in the general election would stoke tea party anger and depress activists’ support for Republican candidates across the country, GOP Senate leaders reversed course and pledged their support to the surprise primary winner after vowing to walk away from Delaware if Rep. Mike Castle was not the nominee.

O’Donnell’s checkered past and stalwart conservatism are viewed as major political liabilities in the heavily Democratic First State.

“We’re sending a message that we’re all on the same team and that Republicans in Washington are listening,” one D.C.-based GOP campaign operative said. “This was an unnecessary and unwelcome distraction.”

“It’s important in all this that we remember that these are elections and voters speak,” Senate Republican Policy Committee Chairman John Thune (S.D.) added. “We live in a democracy. We may not always agree with their verdict, [but] they have weighed in. They’ve made their voices heard in these primary elections, and I think that we should take that very seriously. We ought to take it to heart.”

Senate Republican leaders recruited Castle to run for Vice President Joseph Biden’s old seat as they searched for a candidate capable of winning.

Though a Republican, Castle is a moderate and a popular politician in the state. He was heavily favored in the Nov. 2 general election against New Castle County Executive Chris Coons (D), who is now the favorite to beat O’Donnell.

It is standard practice for the National Republican Senatorial Committee — and any national party campaign committee — to cut underdog candidates loose and focus its money and attention on winnable races. But after the NRSC signaled Tuesday night following O’Donnell’s victory that it would do just that, tea party activists and many popular conservative talk-radio hosts erupted in anger at the party establishment and vowed retribution.

Cornyn Moves Quickly

By late Wednesday morning, the bubbling rift was subsiding as word spread that NRSC Chairman John Cornyn (Texas) had telephoned O’Donnell and promised her the committee’s full support, including a check for $42,600, the most federal law allows it to donate to a campaign. Later Wednesday, Cornyn’s fence-mending efforts continued, with an appearance on the radio show of Fox News Channel personality Sean Hannity, who has been among O’Donnell’s staunchest supporters.

[IMGCAP(1)]”We respect the choice of the primary voters,” Cornyn told reporters Wednesday afternoon. Minority Leader Mitch McConnell (R-Ky.) also announced his support, as did Sen. Scott Brown (R-Mass.), a popular guest attraction on the GOP campaign trail this year.

For Republican leaders attempting to grow their ranks in Congress, the challenge this cycle and in 2012 is to harness the energy of the conservative and decentralized tea party movement without alienating moderate Republicans, independents and soft Democrats contemplating crossing party lines.

Some Republican lawmakers and strategists have expressed concern that if the GOP becomes defined by tea-party-style conservatism and rejects moderates in primary elections wholesale, it could turn off swing voters and hamper efforts to build House and Senate majorities — and win the White House.

But, at least this year, Republicans have the advantage of sharing with the tea party an agenda that calls for reducing government spending, bringing down the national debt and enacting free-market policies focused on job creation and economic growth. Those same issues are resonating with moderates and independents, leaving Republicans confident that tea party activism remains a net plus for them — even though it appears to have cost them the Delaware Senate seat.

“I think that the energy they bring can be very useful to Republicans in the fall,” Thune said. “If you look at the issues people are voting on, it’s basically an indictment of the Democrat agenda.”

Some in the GOP are urging caution in how the party tries to harness the power of the tea party movement. For example, Senate Minority Whip Jon Kyl said the GOP establishment should not try to direct tea party political activism.

“Believe me, you’re not going to be able to manage that energy,” the Arizona Republican said. “What you have to do is understand it, be in sync with it — but you’re not about to manage that energy and I think it’s a big mistake to think that you could.”

Tough Fight Ahead

O’Donnell begins the general election campaign facing an uphill climb.

A recent poll by the Democratic firm Public Policy Polling showed her trailing Coons 50 percent to 34 percent. Additionally, Democrats are sure to attack O’Donnell for a series of false statements, including those regarding her past employment and level of education, and allegations that she has used campaign funds to cover personal expenses.

Regardless, GOP operatives in Washington note that O’Donnell has become a symbol to tea party activists that are set to vote heavily Republican in the November elections, and they worry that spurning her could prove costly. One Republican lobbyist closely monitoring Senate races cautioned that ignoring O’Donnell could be interpreted as the establishment attempting to manipulate elections, creating a rift that could ultimately boost the Democrats.

“Its not a good idea to completely abandon our primary winner. It might impact turnout in more places than Delaware,” the lobbyist said.