Fans hold an American flag during a baseball game at Nationals Park in Washington, D.C., July 4, 2014. Mitchell Layton/Getty Images

What has long been assumed can now, according to most, be made official: The 2016 general election will feature a showdown between the now presumptive Democratic nominee Hillary Clinton and her Republican counterpart, Donald Trump. As six states held primary votes Tuesday, Clinton secured key victories in California, New Jersey, South Dakota and New Mexico, opening up a commanding lead in both pledged delegates and superdelegates.

While U.S. Sen. Bernie Sanders of Vermont has vowed to keep fighting — at least for now — Clinton shifted her focus away from her Democratic competitor in her victory speech Tuesday. "The stakes in this election are high, and the choice is clear," she said. "Donald Trump is temperamentally unfit to be president and commander in chief."

Here are five quick points about the presumptive matchup drawn from recent polls:

On average, it's tight:

The RealClearPolitics average of polls shows Clinton leading by a very slim margin. She's garnering 39 percent support, compared with 38 percent for Trump and 8.5 percent for Libertarian candidate Gary Johnson.

One poll showed Clinton with a significant lead

An online Reuters/ Ipsos survey released Tuesday found 44.3 percent support for Clinton, compared with 34.7 percent support for Trump and 20.9 percent who said they wouldn't vote for either. The poll has had Clinton in the lead for most of the year and included 1,261 respondents, with a margin of error of plus or minus 3.2 percentage points.

Johnson is an unknown — and getting support

A Morning Consult poll released Tuesday found that the Libertarian could be gaining support simply because Clinton and Trump are both historically unpopular nominees. He registered 10 percent support despite just 31 percent of those surveyed being able to recognize him as a politician.

Voters aren't satisfied with their choices (but currently lean left)

The latest Investor's Business Daily (IBD/ TIPP) poll found 61 percent of respondents had an unfavorable view of Clinton, and 63 percent felt that way about Trump. But the poll, conducted May 31 through June 5, found that the presumptive Democratic nominee held 45 percent support, compared with Trump's 40 percent.

Swing states are up in the air

A Public Policy Polling survey released Tuesday found that Trump just barely leads Clinton, by a margin of 41 percent to 40 percent, in the swing state of Florida. A Quinnipiac University poll last month found the two candidates were effectively tied in the key swing states of Florida, Ohio and Pennsylvania.