美国有线新闻 CNN 美国总统大选倒计时8周 带你了解竞选总统全过程（在线收听）

We are less than eight weeks away from Election Day in the U.S. and ten days away from the first presidential debate between Democratic nominee Hillary Clinton and Republican nominee Donald Trump.

Several recent national polls are close. They indicate that neither major candidate appears to have a strong advantage. Looking at Ohio and Florida, two critical battleground states, also known as swing states, these are states whose voters could choose either a Republican or a Democratic candidate. They don't tend to vote the same way in every election.

In Ohio, a recent CNN/ORC poll found that Donald Trump had the lead among likely voters with the support of 46 percent. Hillary Clinton had the support of 41 percent. Libertarian candidate Gary Johnson had 8 percent, and Green Party candidate Jill Stein had 2 percent.

In Florida, the same poll found that Trump had the support of 47 percent. Clinton had the support of 44 percent. Johnson had 6 percent. And Stein had 1 percent. The poll's margin of error is 3.5 percent.

Now, there had been questions about the candidates' stances on policies. There had been questions about their health, about how open their campaigns have been with information. One thing there's no question about is that running takes a massive effort.

PAUL STEINHAUSER, CNN CORRESPONDENT: Running for the White House is unlike any other contest. This is the ultimate prize and it's definitely the major leagues when it comes to campaigning.

SUBTITLE: Explain to Me: Running for President.

STEINHAUSER: Everybody thinks the election is in November, but, honestly, that election starts often two years beforehand.

Going to the early voting states, meeting voters, starting to build up a staff. This is a commitment that takes a lot more than just a few weeks.

Running for the White House is no cheap proposition. It takes a lot of money. This time around, we will see maybe a billion-dollar campaign.

Why does it cost so much money to run for the White House? Because it's more than just a state operation. You're running in all 50 states. And it takes a lot of money, not only to build up a staff to reach out to voters, but also the travel, the commercials. We're talking about an immense amount of money.

You don't always be rich to run for the White House. You can have ideas, and if you start generating buzz, well, then the money follows, especially nowadays with the Internet. It is so much easier now to reach out to anybody to raise money than it was in the old days.

To have a successful campaign, you need a pretty large staff, no doubt about it. You have to have people in the early voting states, like Iowa, New Hampshire, South Carolina, Florida and Nevada. People who are reaching out to voters, people who are setting up events for the candidate.

When it comes to a campaign staff, candidates often like to have young people and old people as well. It's definitely a mixture. Their top strategies are often people who've been around for cycles. But a lot of the younger people out in the states, the volunteers and the fresh faces, those are the people who are knocking on doors and saying hello to voters and trying to spread the message about their candidates.

There are a lot of positions in a campaign, but there are a few people that stand out the most. And one of them will be the campaign manager. That's the person who manages a campaign, basically the boss who decides who does what and where the candidate goes and what the candidate says, to a degree.