With just over six months until Election Day, an analysis of the emerging electoral map by The New York Times found that the outcome would most likely be determined by how well President Obama and Mitt Romney perform in nine tossup states.All nine voted for Mr. Obama in 2008, only to see Republicans make big gains since then.Now, with many of those states transformed economically and politically by the recession, they are perhaps even less predictable than they were in past close elections. The disparity in their circumstances highlights the challenges that both the Obama and the Romney campaigns face in framing arguments that will resonate across the country.The nine — Colorado, Florida, Iowa, Nevada, New Hampshire, Ohio, Pennsylvania, Virginia and Wisconsin — offer both parties reasons for hope, and concern.(...) While the performance of the national economy will help shape the mood of the country and set the tone of each campaign, the situation on the ground in each of the nine states could be pivotal as well.It would be hard to argue that these states are better off now than they were four years ago, given that they have yet to recover the jobs they lost. Often, that makes a compelling argument for a challenger trying to unseat an incumbent.But political scientists have found that past elections have been more influenced by the changes in the economy in the year or two before the election. And a range of economic data provided by Moody’s Analytics shows that all nine states are rebounding and that most now have unemployment rates below the national average. If voters in those states begin to feel the improvement by the fall and the economy does not take a turn for the worse, it could aid the president’s efforts to hold on to enough of them to win.But the length and depth of the recession make it more difficult to model behavior, and the slow recovery could complicate things. Xu Cheng, a senior economist at Moody’s Analytics, which uses state economic and political data to predict election results, said his team had altered its model this year to account for “the grumpy voter effect.”“The so-called grumpy voter effect is that despite economic improvement in a state, if the economic situation in a state is really too bad, the voters will discount the improvement,” Mr. Cheng said. The effect could help tilt foreclosure-racked Florida to the Republicans, he added.(...) The political outlook in the tossup states is far from clear. While they all voted for Mr. Obama in 2008, seven have elected Republican governors since then and all have added significant numbers of Republicans to their legislatures or Congressional delegations. Two states, however, Ohio and Wisconsin, saw Democrats push back strongly after their newly elected Republican governors worked to curb the collective bargaining rights of public worker unions, which could have ramifications in November.(...) Republicans are also making inroads in voter registration. While Democrats retain enrollment advantages in most of the tossup states that register voters by party, their advantage has shrunk in all of them, state elections data shows. Nevada, which had 100,000 more registered Democrats than Republicans in 2008, now has only 35,000 more.The Democratic enrollment advantage has also been reduced in Florida and Pennsylvania. Iowa and New Hampshire, where Democrats held the edge in 2008, now both have more registered Republicans. And in Colorado, the only tossup state where registered Republicans outnumbered Democrats in 2008, the Republicans have widened their edge.In several states, Republicans have recently passed more restrictive election laws, which they say will fight fraud, but which Democrats say will make it harder for some of their key constituencies to vote.Wisconsin and Pennsylvania passed laws requiring voters to show photo identification. Florida tightened the rules on groups that register voters. Several states have cut back on early voting. But some of the new laws are facing court challenges.The changing makeup of the states offers opportunities for both Mr. Romney and Mr. Obama. The share of white working-class voters has increased in Ohio since 2008, which could benefit Republicans, according to an analysis of census data by William H. Frey of the Brookings Institution. Republicans could also benefit from an increase in the share of votes likely to be cast by older white residents in Colorado, New Hampshire, Pennsylvania and Wisconsin.Other demographic trends are likely to benefit Democrats: minorities make up a greater portion of the electorate in Florida, Nevada, Ohio, Pennsylvania and Virginia than they did four years ago; and the portion of white college graduates has grown in Colorado, New Hampshire and Wisconsin. The number of voters ages 18 to 29, a group that helped fuel Mr. Obama’s victory four years ago, is rising in Colorado, Florida, Iowa and Nevada.The map of tossup states is likely to change, and it inevitably involves judgment calls. The Times analysis currently considers Michigan to be leaning toward the Democrats, despite recent Republican gains there, in part because the state benefited from the administration’s bailout of the auto industry.North Carolina, on the other hand, is ranked as leaning Republican, despite the fact that the Democrats have chosen to hold their national convention there this summer.