"Are you better off than you were four years ago?"

As 2012 dawns, the question posed by Ronald Reagan in 1980 is still relevant, especially to the seven Republicans who would like to take President Barack Obama's place in the White House. The race for the presidency shifts into high gear on Jan. 3, when Iowans cast the first votes of the presidential nominating season. A primary marathon unfolds after that, with votes cast state by state, well into the spring. While the Republicans fight to the finish, Obama has drawn a bye in the primaries with no Democratic opposition.

See also: Meet the GOP presidential candidates.

AARP's coverage of Election 2012 includes profiles of the candidates, with an emphasis on where they stand on issues that most matter to older Americans, and video interviews with some of them that cover four of those issues: Social Security, Medicare, jobs and the economy, and retirement security.

Now it's time for the voters to speak. Here are 5 key things to keep in mind as the presidential primaries unfold:

50-plus voters count. It's a political truism that older Americans turn out to vote in much higher percentages than younger voters. It's even truer in primaries and caucuses. That leaves the nominating process in the hands of the most politically active and engaged citizens, most of whom are older and vote regularly. In Iowa in 2008, 73 percent of caucus-goers were 45 or older; in South Carolina, 68 percent of primary voters were over 45. That's clout.

It's all about delegates. The Republican and Democratic parties have elaborate rules that guide their nominating processes. National polls show former House speaker Newt Gingrich and former Massachusetts governor Mitt Romney at the head of the GOP pack, running just about even, with Rep. Ron Paul in third position. All the other candidates are in single digits.

But guess what? The national polls don't matter because the byzantine nominating process is a state-by-state endurance contest. The results in each state determine how many delegates are pledged to each candidate, and while some states allocate delegates on a proportional basis, others are winner-take-all contests. According to AP Elections Research, it will take 1,144 delegates to clinch the GOP nomination, which will be bestowed at the Republican National Convention in August.

Next: Why money matters. >>