Polls go up and polls go down. That's a common refrain from politicians, usually from those with sinking numbers. But it could be said today by either President Barack Obama or Republican Mitt Romney in a clearly tightening presidential race — but one with conflicting poll numbers.

Since Rick Santorum abandoned his GOP bid on April 10, nearly all major polls show a close national election matchup at the outset.

Some give Obama a slight lead, others Romney. A New York Times poll has a dead heat at 46 percent.

Gallup shows Romney ahead, 48 percent to Obama's 44 percent. A Fox News poll gives Romney a 46-44 advantage. But a Pew poll gives Obama the lead, 49 to 45. And a Quinnipiac survey has Obama up 46-42.

An ABC-Washington Post poll shows Obama ahead by 51 to 44 — but it was conducted before Santorum's withdrawal.

That exit made Romney the presumptive nominee.

It's still a long time before the Republican convention in Tampa, Fla., in late August and the Democratic one in Charlotte, N.C. in early September. So voter moods can change.

Right now, polls consistently show the economy as the top issue. Romney runs about even with Obama on his handling of the economy. The president lags on several other issues tested.

Given recent trends, Obama can point to a gradually improving outlook and Romney can cite his experience as a business leader and appeal to those concerned about their own financial plight.

Obama still enjoys a big gender-gap advantage. And the polls show both Romney and Obama are strongly supported by their respective partisans. In most polls, Romney fares well among independents, although not decisively so.

Of course, a lot more ups — and downs — lie ahead.