4 US states to hold primaries Tuesday ahead of November midterms

Americans in Maine, Nevada, North Dakota, and South Carolina will cast votes Tuesday in primary races for seats in the US House, Senate and governor's mansions.

Perhaps no race is being more closely watched than the Senate race in Maine where incumbent Republican Sen. Susan Collins is running unopposed for her party's nomination in November's midterm elections. Newcomer Graham Platner is seeking to end Collins' 30-year Senate career.

Gov. Janet Mills suspended her Democratic campaign earlier this year as Platner continued to gain traction, but remains on the ballot.

While Platner, a progressive Democrat and oysterman, remains the overwhelming favorite to lock in the Democratic nomination, a series of controversies has seen him repeatedly having to defend past mistakes and acknowledge a history of Post-Traumatic Stress Disorder stemming from his time in the military, and alcohol abuse.

Most polls have Platner defeating Collins narrowly in a head-to-head race. That is critical because Democrats are seeking to wrest control of the Senate from Republicans, and if they want to do so Collins' seat is critical.

A UMass Lowell/YouGov poll released on June 2 showed Platner ahead of Collins by 5 points - 48% to Collins' 43%.

Meanwhile in South Carolina, there is no clear front-runner for the governorship even after US President Donald Trump formally endorsed Lt. Gov. Pamela Evette. She is facing stiff competition from Attorney General Alan Wilson with Rep. Nancy Mace also in the race.

A run-off is widely-expected, but eyes are focused on the race as yet another test of Trump's pull among Republican voters amid dour national approval ratings for the US president.

Nowhere is that more pronounced Tuesday night than in Nevada where Republican Gov. Joe Lombardo is having to compete against strong headwinds caused by popular opposition to Trump's policies that have stifled tourism in the heavily-reliant state.

Democratic Attorney General Aaron Ford is currently seeking to capitalize on the discontent, but is facing a significant challenge from Washoe County Commissioner Alexis Hill.

While Lombardo is all but certain to emerge with the Republican nomination Tuesday night, he will face a far more difficult contest to continue his hold on the governorship come November.