MANASSAS, Va. -- Gov. Bob McDonnell on Tuesday finally made an appearance on the campaign trail for Republican U.S. Senate candidate George Allen, who is running out of time in a hotly contested race.

Joining Allen for the first time since June, McDonnell found himself in the somewhat awkward position of attacking Democrat Tim Kaine on looming defense cuts -- an issue McDonnell and Allen once took opposite sides on.

McDonnell and Kaine both supported an agreement to raise the debt ceiling last year that put in place a supercommittee charged with finding $1.2 trillion in spending cuts. The committee failed, and the federal government is now poised to cut about $500 billion in military spending.

Allen rejected that initial deal and repeatedly criticizes Kaine for supporting it.

"I was opposed to this deal because I saw the potential harm if that commission failed," Allen said Tuesday at a Manassas defense contractor.

Minutes later, McDonnell said "nobody expected" the supercommittee to fail. McDonnell was instead critical of Kaine for putting forth a plan to replace the defense cuts partly by raising taxes on high earners.

McDonnell's presence on the trail is aimed at countering Kaine's support among Virginia's moderates. And he is a tough target for the Democratic candidate. McDonnell remains popular with a majority of Virginians, and Kaine has built his campaign on healing partisan wounds in Washington -- two factors that make it difficult for Kaine to return McDonnell's fire.

Kaine's campaign on Tuesday declined to comment on McDonnell's attacks.

Kaine was also left answering for his own party's standard bearer after Monday's final presidential debate. After Republican challenger Mitt Romney accused Obama of scaling back the country's naval fleet, Obama shot back, "We also have fewer horses and bayonets because the nature of our military has changed."

It was one of Obama's sharpest responses, but it could have political ramifications in Virginia, home of the world's largest naval base. McDonnell condemned the comment and accused Obama of not understanding the nature of the military.

"This is how we deploy our men and women quickly to tough spots," McDonnell said, "And he is somehow making an analogy that because we don't have as many horses, we don't need as many ships."

Kaine straddled the issue Tuesday. He voiced support for "modernization and technological advancements" of the country's military forces but noted his own efforts to support Virginia's naval interests, calling them "good for our nation's defense and good for Virginia jobs."

Kaine and Allen are deadlocked in a closely watched Senate race. Because of the state's large military presence, the defense budget has dominated much of the conversation between the two candidates heading into the final two weeks of the campaign.