HARRISBURG — Conservative groups opposing Democratic President Barack Obama on Wednesday poured more money into Pennsylvania, a top electoral prize, amid doubts about whether Republican Mitt Romney has a realistic chance of winning the state.

With the election on Tuesday, two groups that support Romney began running ads, on top of three others that started in recent days.

Americans for Prosperity said it will spend $1.5 million while American Crossroads said it will spend $1.2 million.

Including new ads by the Romney campaign and three other groups that support Romney — Restore Our Future, Americans for Job Security and the Republican Jewish Coalition — television ad spending in Pennsylvania will heavily favor Romney as the campaign enters its final days.

Romney hadn’t aired any TV ads in the state since early April when he was still fending off a primary challenge from former U.S. Sen. Rick Santorum.

But the Romney campaign’s political director, Rich Beeson, said Wednesday that Pennsylvania has become an “interesting” place for the campaign to compete more vigorously. Polls that have favored Obama all year have narrowed in recent weeks, and Republicans have requested more absentee ballots — 142,000 to a little less than 127,000 — than Democrats. They’ve also returned more: almost 89,000 to less than 62,000.

But Beeson also suggested that the campaign does not see Pennsylvania as a crucial building block for Romney to get the 270 electoral votes necessary to become president.

“Pennsylvania is a place we decided to wade into as a path to 300 electoral votes,” he said.

On Wednesday, the Obama and Romney campaigns both characterized the other as desperate and in danger of losing in states crucial to their chances of winning. Obama campaign manager Jim Messina said he was confident the president will win Pennsylvania.

Victory in Pennsylvania is probably more crucial to Obama than Romney. Harry Truman in 1948 was the last Democratic presidential candidate to lose Pennsylvania but win the election, while Republican George W. Bush lost Pennsylvania twice — in 2000 and 2004 — on his way to two terms as president.

Over the summer, the Obama campaign and a handful of Republican political groups spent millions of dollars on TV ads, but those ads disappeared in August amid Obama’s strong performance in independent polls.

Obama still leads in Pennsylvania polls, but those leads have narrowed. On Wednesday, Franklin & Marshall College issued a poll that showed Obama with 48 percent support from registered voters to 44 percent for Romney. The sampling margin of error was plus or minus 3.4 percentage points. The same pollster showed Obama leading by 11 percentage points in September.

Romney has visited Pennsylvania once since mid-July. Obama hasn’t visited since July 6.