Washington ? While many people will work on their tans this summer, or on summer reading lists or on not working too hard, two exceptions – John McCain and Barack Obama – and their underlings will be working.

Working industriously on an election that only one can win.

With 11 weeks to the start of the Democratic convention – and the GOP event just days later – Republican McCain and Democrat Obama will be focused on strategy, fundraising, shoring up weak spots and exploiting opportunities to prepare themselves for the sprint to Nov. 4. They have several issues to worry about.

The electoral map

From now on, the great majority of Americans can be excused if they barely realize a presidential election is under way. They will see virtually no TV ads, visits by candidates or local news coverage.

That’s because this campaign, like the last two, will focus on about 15 competitive states. Both parties see the other states as reliably in their camps and not needing attention, or totally out of reach and not worth the effort and expense of trying to win them. In either case, these states will largely be ignored.

McCain will start by trying to hold the 31 states President Bush won in 2004 (which are almost identical to the 30 he won in 2000). If he succeeds, he will be president.

Obama must claim one or more of those states, while losing few if any of the ones Al Gore and John Kerry won in their narrow losses to Bush.

The magic number is 18. That’s how many electoral votes Obama must add to Kerry’s 252, from four years ago, to secure the presidency. For example, if Obama carries Iowa (seven electoral votes) and Missouri (11) without losing any Kerry states, he would become president.

Other states Obama will target as possible pickups are Florida, Ohio, New Mexico, Nevada, Colorado and at least one – Virginia – not normally within the Democrats’ reach.

Running mates

Analysts question whether a vice presidential choice seriously affects a presidential election, but Obama calls it the most important decision he will make before Election Day. He and McCain have appointed small groups to vet contenders and, if nothing else, the process will fascinate the political chattering class for a while.

Obama first must decide whether to tap Sen. Hillary Rodham Clinton, who battled him to the end and has legions of fans who want her on the ticket. Many political insiders think he will turn elsewhere, but they do not agree on a front-runner.

Possibilities include four vanquished presidential rivals (besides Clinton): New Mexico Gov. Bill Richardson, former Sen. John Edwards of North Carolina, and Sens. Joe Biden of Delaware, and Chris Dodd of Connecticut. Former Sen. Sam Nunn of Georgia is often mentioned, as are two prominent female supporters of Obama: Sen. Claire McCaskill of Missouri and Kansas Gov. Kathleen Sebelius.

McCain is likely to look at Republican Govs. Tim Pawlenty of Minnesota and Charlie Crist of Florida, two battleground states. Other possibilities include former Massachusetts governor and presidential rival Mitt Romney; Utah Gov. Jon Huntsman; South Carolina Gov. Mark Sanford; Alaska Gov. Sarah Palin; and former congressman and White House budget director Rob Portman of Ohio, another key state.

Defining the opponent

Campaign pollsters say the average person still knows relatively little about Obama or McCain. Both men and their allies will race to fill in the blanks with appealing portraits of themselves and unflattering pictures of the other.

Obama’s theme is “change,” and he constantly says McCain would carry out “a third term” of President Bush, whose approval ratings approach historic lows. McCain portrays Obama as inexperienced, naive and more talk than action.

Youth and age will be a key subtext. Obama does not directly allude to McCain’s age, which will hit 72 on the eve of the GOP convention. But their age difference, 25 years, is the largest in history for major party nominees. Obama must show he’s mature and ready; McCain must show he’s sharp and vigorous.

Both campaigns are rapidly adding staff. Obama’s team will focus on introducing the first-term senator to voters who may not know much about his biography, while today he begins a two-week economic tour of the country.