There are warning signs in the new CNN/Des Moines Register Iowa poll for both former Vice President Joe Biden and California Sen. Kamala Harris.

Biden is still atop the poll, but by a narrower margin than in national polling, and his supporters are less likely to be "extremely enthusiastic" about his candidacy. For Harris, just 7% of likely caucusgoers choose her as their top pick -- the latest example of her stagnant poll numbers.

New York Times national political correspondent Jonathan Martin reports that both candidates recognize the need to perform in Iowa and plan to ramp up their time on the ground there.

"Joe Biden, if he loses Iowa, it's going to be a blow to his campaign, simply because he is the frontrunner," Martin said.

For Harris, it's more about the long game.

"She needs oxygen coming out of the early states to get to places like South Carolina," Martin said. "You've got to get a win or close to a win somewhere, and Iowa could be her best shot to do that."

2. An alternative to candidate fundraisers? Cardboard candidates

Presidential campaigns run on donations, and so far this cycle, the amount raised by individual candidates has become a major indicator of a campaign's viability.

With the second quarter of 2019 coming to a close, Washington Post national political reporter Annie Linskey reports that some campaigns find themselves caught between pledges to steer clear of big donors and making ends meet.

"The second quarter is going to show the durability of some of these candidates in this giant field," Linksey said. "A lot of them have been trying to go with small donors but are learning pretty quickly that that's not raising enough money."

One candidate who has stuck to her pledge to avoid large dollar fundraisers: Elizabeth Warren. But Linskey reports that while the Massachusetts senator has kept her pledge to avoid large dollar fundraisers, some of her supporters are growing anxious and are looking for new ways to raise funds, like having the candidate Skype into events.

Warren has so far rejected that idea, but Linskey said that's not deterring her supporters.

"I was talking to one donor," she said, "who was saying that they might actually have a cardboard cutout of the senator" at events instead of the real thing.

3. Florida, Florida, Florida

The Sunshine State invariably plays a key role in every election cycle, and 2020 is shaping up to be no different. But as AP Washington bureau chief Julie Pace reports, Democrats are "really confounded" by what to expect from Florida next year.

"Even after Florida tilted to (President Donald) Trump in 2016, a lot of Democrats were still really rattled by the way the state performed in the governor and Senate races in 2018," Pace said.

In the run-up to those elections, Democrats hoped that Tallahassee Mayor Andrew Gillum and Sen. Bill Nelson would win over their Republican opponents. Instead, both were defeated by narrow margins. Now, the party is trying to figure out how to avoid a repeat in 2020.

"The gains in Florida, the promise in Florida, is simply too big against Trump," Pace said. "You could effectively knock him out if you could win there. They just aren't quite sure they have a path to doing that right now."

4. Surviving a GOP primary in the Trump era

North Carolina Sen. Thom Tillis is one of Trump's staunchest allies in the Senate. Most recently, he was one of the few Republicans to defend the President's threatened tariffs against Mexico.

CNN senior congressional correspondent Manu Raju reports that it's all about 2020 politics.

"Tillis is someone who could face a primary threat in 2020," Raju said, pointing to a potential primary challenge from Rep. Mark Walker.

Tillis got a taste of the risk that comes with breaking with Trump in today's GOP earlier this year, when he was roundly criticized for initially coming out against the President's border wall emergency declaration. Since then, he's been solidly on Team Trump.

"It's all a sign," Raju said, "that primary politics is about who defends the President the most."

5. Trump's Changing GOP

And from CNN chief national correspondent John King:

The last-minute deal between the Trump administration and Mexico means no new tariffs on Monday. It also means we will not get to test the promise of Senate Republicans to try to block Trump had he acted on his tariff threat

Still, the verbal revolt was a reminder of how much the Republican Party is changing during the Trump presidency, and a reminder that those changes are testing traditional GOP alliances heading into an election season.

One example this past week: word that the Koch family's political network is looking to change how it operates.

The Koch brothers spent tens of millions of dollars the past two decades helping Republicans. But the Koch network is no fan of Trump because of his policies on trade and immigration and what the Kochs see as a failure to deliver on conservative promises of smaller and more efficient government. The frustration extends to Republicans, supported by Koch groups like Americans for Prosperity in the past, who are reluctant to stand up to President Trump.

So look for a shift in 2020. CNBC was first to report a new strategy memo that says, "AFP or AFP Action will be ready to engage contested US Senate, US House, and state-level primary races, including Republican, Democrat, Independent or otherwise, to support sitting legislators who lead by uniting with others to pass principled policy and get good things done."

To be clear, some of that support of Democrats could be to help more moderate and establishment incumbents fight off challenges from liberal activists. So there is no evidence the Kochs will suddenly be targeting Republicans. But any retreat from supporting Republicans is of concern to GOP strategists looking at uncertain 2020 House and Senate maps. The reasons behind the Koch shift, alone, highlight the frustration among those whose allegiance with the GOP was born of shared interest in free market economics and a more welcoming immigration perspective.

Another test is now moot because of the weekend deal with Mexico. But had it not been reached, the Chamber of Commerce, an icon of the GOP establishment, was preparing to file a lawsuit against the Republican administration challenging the Mexico tariffs plan.

The Chamber's political arm puts protecting the GOP Senate majority atop its 2020 goals. Still, the Chamber, too, is alarmed with the drift -- or shift -- of the GOP under Trump on trade and immigration issues.