As the song goes, you ain't seen nothing yet.

Sen. Joe Donnelly and Republican Mike Braun already have blitzed Indiana with campaign stops, political advertising and big-name rallies. But in the final push toward Election Day, the airwaves are about to get even more crowded with campaign commercials touting and bashing the two candidates.

With party control of the U.S. Senate at stake, the money will continue to flow and the national spotlight will continue to shine on Indiana's pivotal race. The candidates and outside groups have committed $36.4 million on advertisements for Sept. 30 to Nov. 6, among the highest in the nation's Senate races, according to a USA TODAY analysis of data from Kantar Media/CMAG.

Republican insiders believe President Donald Trump and Vice President Mike Pence will return to Indiana in the coming days to stump for Braun. The administration needs the state to deliver another win and Republican insiders say Pence would be loathe to let Indiana's Senate seat stay blue.

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Donnelly, on the other hand, seems likely to continue to shy away from big-name liberals, as he did when Sen. Bernie Sanders campaigned in Bloomington earlier this month. Expect Donnelly, who campaigned in Indianapolis that day, to crisscross the state in his 16-year-old RV while name dropping Republicans he's worked with, including Trump himself.

Donnelly is walking the political tightrope successful Democrats must navigate in red-leaning Indiana — sounding conservative enough to reach moderate Republicans and progressive enough to motivate his base.

While the personable Donnelly thrives in front of crowds, his opponent, a millionaire businessman from Jasper, is less of a natural campaigner. Braun has used an aggressive barrage of advertisements to shape his public image as a reliable Republican who will back Trump.

Indiana is an unlikely battleground. Republicans control every executive office in state government and enjoy super majorities in both chambers of the Indiana General Assembly.

For most of the past decade, the R beside Braun's name would be enough to assure victory.

But then, Donnelly is an unlikely senator.

He was given little chance to win 6 years ago. But he seized the opportunity when conservative Republicans ousted the highly venerated Richard Lugar in the GOP primary and replaced him with Richard Mourdock, who subsequently imploded by describing rape at a televised debate as "something God intended."

Republicans figured Donnelly would be a one-off senator and have been lining up to replace him for six years. Braun won that right after defeating two congressmen who are now looking for new jobs.

Polling, though, repeatedly has shown Donnelly and Braun statistically tied, with a large chunk of undecided voters. Neither candidate has been able to pull ahead, and neither has done something to lose the race.

So who's the smart money on?

Democrats are hoping the Trump administration's policies and tone trigger a blue wave across the nation. History shows the midterm generally favors the minority party. Democrats think that momentum, coupled with Donnelly's pragmatic approach, will win a second term.

Republicans believe any blue wave will break against the red rocks of Indiana.

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The past two years have proven Trump's appeal should never be discounted, especially in Indiana. The president also has been working to shore up Republican votes by talking about immigration, tax cuts and border security, repeatedly focusing on a migrant caravan a thousand miles from the Texas border.

"We have two competing currents taking place," said Robert Dion, a political science professor at the University of Evansville. "In a normal year, the state would lean Republican. But the trend nationally favors Democrats. We are about to see which of those winds prevails, and I think it's going to be awfully close."

Trump will play a role

Braun is banking on the popularity of Trump with most Hoosiers to get over the finish line first. Donnelly, though, has moved to blunt that advantage by aligning himself with the president on some key issues, including supporting the border wall.

The president was in Indianapolis Saturday at the national Future Farmers of America convention, reassuring jittery farmers that his trade battle with China will turn out well for them.

Republicans believe the president will return to Indiana to hold one more rally for Braun before the race is over. They think it's likely Pence will visit too.

Trump won Indiana by 19 percentage points and pundits think he'll energize the Republican base. But it's unclear whether he will motivate undecided voters.

"I think that the rallies certainly get people ready to go," said Andy Downs, political science professor at Purdue University Fort Wayne. "Part of the question becomes is this actually moving voters who aren’t already with Braun."

Donnelly clearly is trying to prevent Trump from becoming the deciding factor in the race. The senator likes to say he votes with Trump 62 percent of the time — when the president does things that sync with Indiana.

Donnelly's strategy was highlighted in a news release his Senate team issued last week. Donnelly's staff touted the fact the president signed a bipartisan bill to fight opioid abuse, a key campaign issue for Donnelly, that included several provisions the senator says he pushed.

"I'm very glad the president signed the SUPPORT for Patients and Communities Act into law," Donnelly said in the news release. "This gives us more tools to combat this public health crisis."

A Democrat issuing a statement like that about Trump just before the election is rare in these times.

"What Donnelly is doing is unique on a national level," Downs said, "but in some ways it is what a Democrat has to do to win a statewide election in Indiana. "

Donnelly seems unlikely to bring in heavy hitters of his own.

Former Vice President Joe Biden held a rally with the senator earlier this month in the northwest Indiana steel city of Hammond, comfortably far from the moderate voters he'll need to reach in suburban Indianapolis.

What's up with those ads?

In person, Braun and Donnelly come off as level-headed nice guys, and neither has a penchant for doing or saying radical things.

Their advertisements, though, tell a different story. They have each tried to paint the other as a partisan extremest who would represent national political interests instead of Hoosiers.

Republicans call the senator "Mexico Joe" after saying his family business outsourced jobs to Mexico. They claim he represents Washington D.C. interests, has lost touch with Hoosiers and sides with liberals when it matters.

Democrats have labeled Braun as bad for Indiana, claiming his company buys parts from China, mistreats workers and has poor health-care coverage.

Donnelly and Braun, of course, each blamed the other side for the negatives ads. Each said they'd rather the campaigns were run on the issues.

“What kind of person would I be if you throw a fastball at my head and I just lay down at home plate?” Donnelly asked. “I’m going to fight for myself. I’m going to fight for our state. I’m going to fight for our country. And If you throw one at me, I’m going to throw one right back at you.”

Braun said negative campaigning discourages people from running.

"It ought to be your rèsumè and what are you going to bring to the table," he said. "What are your solutions?

There's a reason things got so negative so quickly — it works.

Former Democratic Sen. Evan Bayh entered the 2016 Senate race as the presumed front runner but didn't react swiftly enough when Republicans unleashed a torrent of negative advertisements defining him as a rich carpetbagger who would side with liberals.

Bayh eventually launched his own onslaught, but too late to recover. Republican Todd Young defeated him 52 percent to 42 percent.

Donnelly and Braun have both run advertisements to ensure they won't be redefined.

Donnelly raised eyebrows when his campaign featured one TV add showing the senator chopping wood with an ax and criticizing the “liberal left” for wanting to reduce defense spending. Another said he'd defend Hoosiers from "socialists" and the “radical left" seeking to establish government-run health care and abolish I.C.E., the Immigration and Custom Enforcement agency.

"Over my dead body," Donnelly says in the advertisement.

Braun has responded to the attack ads against his business practices by running advertisements that defend his company.

He boasts in his one campaign ad that his business is “proud to be made in America" and the company “treats folks like family.”

There's more to come

Neither candidate will run short of cash to spend, so expect the TV, radio and digital barrage to continue.

Donnelly raised $4.6 million from July 1 to Oct. 17. He has $2.32 million more to spend.

Braun has loaned his campaign nearly $4 million through the same period. He raised another $4.5 million and has $1.3 million left to spend.

And that's not all. Outside cash has flowed in. Campaigns get more bang for their buck when purchasing advertising from their own cash, due to federal rules, but there's no question the outside spending has been noticed.

Super PACs have spent $8.8 million and the Democratic Senatorial Campaign Committee has spent $5.2 million to support Donnelly, according to the USA TODAY analysis.

Super PACS have spent $9.9 million to back Braun and the Republican Senatorial Campaign Committee has spent $2.3 million, USA TODAY reported.

The data includes advertisements that will run through the election on Nov. 6, so those numbers will change if outside groups purchase more ad time.

Hit the road

Pundits say Braun and Donnelly will continue to exchange blows in political advertisements down the final stretch to avoid losing ground, but the reality is neither is likely to move opinion significantly with commercials at this point.

One chance to win over voters will come Tuesday night when Braun and Donnelly face off in their final debate, along with Libertarian Lucy Brenton, at 7 p.m. in Indianapolis.

But it would probably take a major mistake by one of the candidates to have an impact on the race. Now, it's really about how hard the two campaigns work directly to get their own voters to the polls and reach the remaining independents.

There's still a core group of undecided voters — 11 percent in the recent Mike Downs Center for Indiana Politics at Purdue University Fort Wayne poll — and Braun and Donnelly are trying to win over as many as they can by touring the state nearly non-stop this week.

"It's so tight right now that every ounce of energy is necessary," said Dion, the Evansville pundit, "and the people who are better organized and more motivated are likely to win by a small margin."

Braun is stumping this week with Gov. Eric Holcomb on the Indiana GOP's Right Track Tour which plans stops in Elkhart, Howard, Johnson, Marion, Boone, Tippecanoe, Lake, St. Joe, Koscuisko and Hamilton counties.

His campaign will continue to push the message he is a political outsider with real-world business experience, similar to Trump.

After winning a primary decided by who could appear the most Trump-like, Braun has made a late, and slight, shift to the center. He said he doesn't think the president's tariffs on China are sustainable into next year, worrying farmers especially will feel the impact.

Donnelly will be campaigning throughout the state as well, focusing on his hometown area of South Bend, plus Lake County, Indianapolis and its suburbs.

His campaign will reinforce his image as someone with a pragmatic approach who crosses party lines to get things done. Donnelly thinks the race will be won by who directly reaches the most voters.

Both sides say they've got their bases motivated to vote. Both sides plan to campaign throughout the Indy area, especially the suburbs, down the stretch to reach those last undecided or unmotivated voters.

"This is really about independents," Downs said, "it's about moderates, it’s about people who might be not the most consistent voters."

Call IndyStar reporter Chris Sikich at 317-444-6036. Follow him on Twitter: @ChrisSikich and at facebook.com/chris.sikich.

Call IndyStar reporter Kaitlin Lange at 317-432-9270. Follow her on Twitter: @kaitlin_lange.