(CNN) -

American voters are divided on whether they want the GOP to win control of the Senate in November's elections, according to a new national poll.

And a Quinnipiac University survey also indicates the race for the 2016 Republican presidential nomination remains a free-for-all among the potential contenders, while Hillary Clinton, if she runs for the White House again, would be the prohibitive frontrunner for the Democratic nomination.

The poll's Tuesday release comes with the midterm elections just under four months away. It indicates that 46% of registered voters want the Republicans to win control of the Senate, with 44% saying they want the Democrats to retain control of the chamber. By the same slight 46%-44% margin, voters want to see the GOP keep control of the House of Representatives.

In the generic ballot question, the Democrats have a narrow two percentage point (41%-39%) edge over the Republicans among registered voters. The generic ballot asks respondents to choose between a Democrat or Republican in their congressional district without identifying the candidates.

Democrats have a 55-45 majority in the Senate (53 Democrats and two independents who caucus with the party). But in the midterms, the party is defending 21 of the 36 seats up for grabs, with half of those Democratic-held seats in red or purple states. In the House, the Democrats need to pick up a challenging 17 Republican-held seats to win back the majority from the GOP.

The poll indicates that voters are giving both parties in Congress a big thumbs down. Seventy-three percent say they disapprove of the job congressional Republicans are doing, with 63% saying they disapprove of the job Democrats on Capitol Hill are doing. Both parties favorable ratings are also underwater.

"Americans are split on whether they want Republican or Democratic wins in the midterms, but on one thing they are in complete agreement - Congress as a whole is doing a lousy job," says Tim Malloy, assistant director of the Quinnipiac University poll.

Race for 2016

Clinton has been the overwhelming frontrunner for the nomination in just about every national and state poll conducted over the past 18 months, and the new Quinnipiac survey is no exception.

According to the poll, 58% of Democrats and Democratic leaning voters say if the their party's presidential primaries were held today, say they'd support the former secretary of state. Sen. Elizabeth Warren of Massachusetts, who says she's not running in 2016, is a distant second at 11%, with Vice President Joe Biden, who's mulling a third White House bid, at 9% and New York Gov. Andrew Cuomo at 4%.

The GOP race remains a wide open affair, as previous polling has indicated. Sen. Rand Paul of Kentucky's at 11% among Republicans and Republican leaners, with New Jersey Gov. Chris Christie, former Florida Gov. Jeb Bush, and former Arkansas Gov. Mike Huckabee, a 2008 GOP presidential candidate, each at 10%. Sen. Ted Cruz of Texas, Wisconsin Gov. Scott Walker and Rep. Paul Ryan of Wisconsin, the 2012 Republican vice presidential nominee, are each at 8%. Sen. Marco Rubio of Florida is at 6%. No other potential candidate listed cracked 3%.

"Former Secretary of State Hillary Clinton takes a ton of heat on wealth, book sales and her legacy at the State Department, but she emerges with no serious Democratic challenger, while the Republican field remains clustered and flustered," Malloy adds.

In potential 2016 general election showdowns, the survey indicates Clinton topping several possible GOP candidates by seven to nine points. The poll also suggests a wide gender gap, with Clinton's lead among women ranging from 16 to 19 points and the margin among male voters is basically knotted.

The poll indicates Clinton with a 48%-43% favorable/unfavorable rating, which tops all other potential Democratic or Republican White House contenders.

The Quinnipiac University poll was conducted June 24-30, with 1,446 voters nationwide questioned by telephone. The survey's overall sampling error is plus or minus 2.6 percentage points.