President Obama will announce former Sen. Chuck Hagel, R-Neb., today as his pick to succeed Defense Secretary Leon Panetta, Democratic sources in the defense community and in Congress tell CBS News - and lawmakers and policy groups on both sides of the aisle are already priming for a confirmation fight.

"I think there will be a lot of tough questions for Sen. Hagel," Senate Minority Leader Mitch McConnell, R-Ky., said Sunday on NBC's "Meet the Press," "but he will be treated fairly by Republicans in the Senate. I think he'll be subjected to the same kind of oversight hearings that any nominee for such an important position would expect."

McConnell said he's waiting out the hearing process and wouldn't commit to voting for or against a Hagel nomination, but said his "views with regard to Israel, for example, and Iran and all the other positions that he's taken over the years will be very much a matter of discussion in the confirmation process."

Indeed, Hagel's record on the Middle East and Israel in particular has attracted strong opposition, mostly from Republicans and the pro-Israel lobby. The Vietnam War veteran branded himself a maverick conservative during his two Senate terms, loudly criticizing the wars in Iraq and Afghanistan, calling for U.S. negotiations with the Palestinian organization Hamas, and voting against some Iran sanctions. After co-chairing Arizona Sen. John McCain's unsuccessful bid for the 2000 GOP presidential nomination, he turned around in 2008 and endorsed Mr. Obama.

Hagel has served as co-chair of the President's Intelligence Advisory Board since 2009, and is also a member of the Secretary of Defense's Policy Board.

"Chuck Hagel, if confirmed to be the secretary of defense, would be the most antagonistic secretary of defense toward the state of Israel in our nation's history," Sen. Lindsey Graham, R-S.C., said Sunday on CNN's "State of the Union." "Not only has he said you should directly negotiate with Iran, sanctions won't work, that Israel should directly negotiate with the Hamas organization - a terrorist group that lobs thousands of rockets into Israel - he also was one of 12 senators who refused to sign a letter to the European Union that Hezbollah should be designated as a terrorist organization."

Graham said he will support Sen. John Kerry, D-Mass. - the president's nominee to replace Hillary Clinton as secretary of state - arguing he is "in the mainstream of thought." Hagel, meanwhile, "is an in-your-face nomination by the president, and it looks like the second term of Barack Obama is going to be an in-your-face term," he said.

Sen. John Cornyn, R-Texas, had similarly disparaging words for Hagel. In a statement out Sunday, Cornyn said he will not support the nomination, as Hagel's "record and past statements, particularly with respect to rogue nations like Iran, are extremely concerning to me. ...As Iran becomes increasingly hostile and gains influence in the region, the worst possible message we could send to our friend Israel and the rest of our allies in the Middle East is Chuck Hagel."