JACKSONVILLE, Fla. (AP) — Reflection over Sept. 11 quickly past, the race for the White House is returning to fierce form, with negative ads free to fly again and the candidates spreading out from Florida to Ohio to Nevada.

In a campaign speech and a new TV ad, President Barack Obama was accusing Republican nominee Mitt Romney of failing to explain how he would pay for trillions of dollars in tax cuts.

Eyeing the possible electoral paths to victory, both campaigns are jockeying more in Wisconsin, a state that has long swung to Democrats in presidential elections.

Romney, in the midst of a campaign week that has slingshot him across the nation, was holding one event today — at his own campaign office in Jacksonville, Fla. He was expected to make the case that the nation’s debt is undermining job creation and economic growth.

Obama was heading west, to Nevada, where he planned to hit Romney and vice presidential nominee Paul Ryan with charges of secrecy. The Obama campaign says the two Republicans are refusing to tell voters how they could pay for tax cuts that disproportionately help the wealthy without having to gut deductions for middle-class taxpayers.

An Obama campaign ad making that point will start running in Iowa, Virginia, Nevada and Ohio. Those four states, plus Florida, New Hampshire and Colorado, continue to draw the most campaign time and money, with others states looming on the margins as possible toss-ups.

One of those is Wisconsin, home state of the Republican lawmaker Ryan, who will be holding a town hall in Green Bay, Wis., today as the race in the state appears to tighten. For the first time, Obama’s campaign was airing TV ads in Wisconsin, starting today. They come after Romney started running his own spots there Sunday.

Ryan and Vice President Joe Biden will also campaign in Ohio today.

Tens of millions of voters in most parts of the United States are not being wooed directly, as their states are already considered to tilt clearly toward Obama or Romney. Obama appears to have more favorable paths to the required 270 electoral votes he needs for a second term, but in a shaky economy, he is in a hard fight.

With 55 days left until the election, Obama and Romney were keeping a steady pace of post-convention events, but hardly one that screamed urgency.

Romney spent much of his Tuesday in the air, flying from the Chicago area to Reno, Nev., for a speech on the legacy of the Sept. 11 attacks before moving onto Florida.

His morning event in Jacksonville is his only scheduled one today.

Obama devoted his Tuesday to Sept. 11 ceremonies in Washington on a day that was stripped of overt campaigning but clearly offered political messages from both candidates. This afternoon, Obama was going to Las Vegas for one economy-themed rally at night before moving on to Colorado for an event there Thursday. Colorado and Nevada are key early-voting states.

Romney was splitting Florida duty with his wife, Ann, who was holding her own rally in Largo; former President Bill Clinton, meanwhile, was to campaign for Obama in Orlando.