Kentucky, Arkansas, Oregon and Pennsylvania voters are preparing to choose their parties' candidates for the mid-term elections
Voters are having their say on the future direction of the Democratic and Republican Parties in four states in primary elections on Tuesday, ahead of November's mid-term ballots. The BBC's Paul Adams meets voters in Little Rock, Arkansas.
In Arkansas, the sitting Democratic senator, Blanche Lincoln, is facing the first primary challenge against an incumbent for 36 years.
On a warm evening, five days before polling day, harmonious sounds waft across an old railway bridge, spanning the Arkansas River at Little Rock.
A quartet from Little Rock's symphony orchestra entertains passers-by at the start of a 10-day arts festival. At the other end of the bridge, a blues band gets into a different groove.
There are tapas and wine to be savoured, while down on the river bank graduating medical students enjoy piles of steaming red crawfish.
Little Rock is showing off its various colours.
'Arkansans weigh in'
Ted Holder is out on the bridge with his long-term partner Joe Vanden Heuvel. Both lifelong Democrats, they have already taken advantage of early balloting and wear stickers saying "I voted".
Not for Blanche Lincoln.
"She acts like such a Republican," complains Ted. "We've had some really good senators from this state, and progressive ones. And man, we just don't have them now. It's sad."
Voters Melba Collins and Gordon Brehm are helping Bill Halter's efforts
And for some, it's not enough just to gripe.
The following morning, I find Melba Collins cooking delicious French toast in the house she shares with Gordon Brehm, three Irish setters, a cat and, for the time being, two members of Bill Halter's campaign team.
Before they retired, Melba and Gordon were both union organisers. Now they are devoting all their time to getting Mr Halter nominated.
Melba says she collared Arkansas's Lieutenant Governor Bill Halter at a Labour Day picnic last year and told him if he ran for Senate she would work for him "till my dying breath".
"And here I am!" she laughs.
And while Melba and Gordon say they like Bill Halter, it is clear they are also hugely motivated by anger over Blanche Lincoln's record.
"She's all sweetness and light when you meet her, but you can't pin her down on an issue," says Gordon. "She tries to be all things to all people. To me, that's the worst thing that a politician can be."
Melba and Gordon call Ms Lincoln "Republican lite" and say that she has sided with Republicans more than with President Barack Obama.
Democratic Senator Blanche Lincoln is facing a challenge from rival Bill Halter
In fact, Ms Lincoln's voting record suggests otherwise, but there have been notable exceptions, including her reservations about aspects of Mr Obama's healthcare reform proposals.
But labour unions and progressive groups across the country, including many who campaigned hard for Barack Obama, have spent millions of dollars on television ads that portray the senator as being too cosy with big money and special interests.
"She has been seen, particularly during the presidency of Barack Obama, as an obstacle to the sort of change that they hoped for," says Professor Janine Parry, political scientist and poll director at Arkansas University.
Ms Parry says the Arkansas race has become emblematic of a bigger national drama.
"How much change will Obama be able to effect? And who is going to be on his team and are Democrats on board enough to get it done, or are they in fact teaming up with the enemy in this very highly polarised environment?"
Bill Halter has urged Arkansas residents to "vote for change"
During a final primary debate in front of 400 people at Little Rock's Statehouse Convention Center, Bill Halter plays, as so many others have this year, on the strong anti-incumbent sentiment stalking the land.
"The choice here is simple," he concludes. "You can continue with the same Washington policies, or you can vote for change."
It is an argument that resonates with some in the room, but there are plenty of Lincoln supporters here too.
"Senator Lincoln has done a lot of good but she's got a tough fight on her hands," says a member of the audience.
"I think she has a good handle on what the American people need," says another, noting Ms Lincoln's current role, as chair of the Senate's agriculture committee, in promoting tough regulation of the derivatives market.
'Banter and hugs'
Later that afternoon, I find the embattled senator in relaxed mode, exchanging easy banter and lots of hugs with veterans of the military, at an event in Little Rock's elegant Capitol building.
"I am a pragmatic politician," she insists, when I put to her the frustrations of people like Melba and Gordon.
"And that means finding common ground."
The daughter of a rice farmer, Ms Lincoln employs an extended metaphor.
"You build a levee around your rice field as it floods, and then you walk that rice levee," she says. "You don't run down the levee because if you run... you bust the levee."
And what do you do when you get all the way round?
"You walk it again."
It may be that walking the levee is simply too moderate for today's bitterly partisan environment, and Ms Lincoln has described herself as the rope in a tug of war.
Perhaps she reflects another difficulty too: that of being a conservative Democrat from the south, with a northern, progressive, black president in the White House.
But with Republicans licking their lips at the prospect of taking her on in November, Tuesday's primary is only the start of her battle for survival.