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Democrat Hillary Clinton leads Republican Donald Trump in three key battleground states after the conclusion of the political conventions, including in all-important Ohio, according to a trio of new NBC News/Wall Street Journal/Marist polls.

In Iowa, Clinton is ahead of Trump by four points among registered voters, 41 percent to 37 percent, with the rest saying neither, other or they’re undecided. (Before the conventions, Clinton was up by three points in the state, 42 percent to 39 percent in last month’s NBC/WSJ/Marist poll.)

In Ohio, Clinton holds a five-point advantage over her Republican opponent, 43 percent to 38 percent. (The two were tied before the conventions at 39 percent each.)

And in Pennsylvania, Clinton has expanded her lead over Trump to 11 points among registered voters, 48 percent to 37 percent. (Her lead was nine points before the conventions, 45 percent to 36 percent.)

“These three states are key ingredients in Trump's formula for success and a region where Trump was hoping [running mate Mike] Pence would provide a boost,” says Lee Miringoff, director of the Marist College Institute for Public Opinion. “Yet Trump is coming up short in his bid to change the electoral map. Given that Clinton has many more paths to the White House, these poll results are a warning sign for the Trump effort.”

Measuring the four-way horserace

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When the 2016 presidential race is expanded to four candidates – including Libertarian nominee Gary Johnson and the Green Party’s Jill Stein – Clinton and Trump are tied at 35 percent each in Iowa, with Johnson at 12 percent and Stein at 6 percent. (Last month in the state, Clinton and Trump were tied in the four-way horserace at 37 percent.)

In Ohio, Clinton gets the support of 39 percent of registered voters, Trump gets 35 percent, Johnson gets 12 percent and Stein gets 4 percent. (It was Clinton 38 percent, Trump 35 percent last month.)

And in Pennsylvania, it’s Clinton at 45 percent, Trump at 36 percent, Johnson at 9 percent and Stein at 3 percent. (The numbers are nearly identical to what they were before the conventions last month.)

Trump, Clinton remain unpopular

The new polls also show that Trump and Clinton remain unpopular in these three states.

In Iowa, 36 percent of registered voters have a favorable view of Clinton, versus 58 percent with an unfavorable view (-22), while Trump is at 31 percent positive, 64 percent negative (-33).

In Ohio, it’s Clinton at 36 percent positive, 60 percent negative (-24); Trump is at 31 percent positive, 62 percent negative (-31).

And in Pennsylvania, it’s Clinton at 43 percent positive, 53 percent negative (-10), and Trump at 31 percent positive, 63 percent negative (-32).

For the most part, these numbers are essentially unchanged from where they were before the conventions.

“Despite the national spotlight of the conventions focused on each candidate, Clinton and Trump have not made any headway in voters’ positive impressions of them,” Miringoff says.

Polling the Senate races

Iowa, Ohio and Pennsylvania also feature some of the more competitive Senate contests of this cycle.

In Iowa, incumbent Republican Sen. Chuck Grassley leads Democratic opponent Patty Judge by 10 points, 52 percent to 42 percent – unchanged from July.

In Ohio, incumbent Republican Sen. Rob Portman is ahead of Democratic challenger Ted Strickland, 48 percent to 43 percent; they were tied at 44 percent each last month.

And in Pennsylvania, Democratic challenger Katie McGinty leads incumbent GOP Sen. Pat Toomey, 48 percent to 44 percent; she was ahead by three points last month, 47 percent to 44 percent.

Finally, President Barack Obama’s approval rating among registered voters stands at 45 percent in Iowa, 49 percent in Ohio and 50 percent in Pennsylvania.

The NBC/WSJ/Marist polls were conducted Aug. 3-7 of 899 registered voters in Iowa (which has a margin of error of plus-minus 3.3 percentage points), 889 registered voters in Ohio (plus-minus 3.3 percentage points) and 834 registered voters in Pennsylvania (plus-minus 3.4 percentage points).