Trump is 'vulnerable' and 'thrashing around' as GOP bristles at his wall shutdown: former presidential adviser
Donald Trump speaks during a campaign rally at the American Airlines Center in Dallas on September 14, 2015 (AFP Photo/Laura Backman)

A former adviser to multiple presidents observed Tuesday that Donald Trump is acting out as the Republican Party fractures over his border wall government shutdown.

Responding to news that 11 Senate Republicans joined Democrats to successfully block Trump's Treasury Department from lifting sanctions on businesses linked to a controversial Russian oligarch, former presidential adviser David Gergen said there may be writing on the wall.

"The Republican unity is cracking on this and on multiple fronts, such as the shutdown," Gergen told his CNN co-panelists.

The Senate's vote to block Treasury from lifting sanctions on businesses linked to Oleg Deripaska, a Russian billionaire who counts former Trump campaign chairman Paul Manafort as a debtor, shows that Trump "is not in command the way he once was," the former presidential adviser said.

"He's much more vulnerable, he's thrashing around," Gergen added. "And all of that is to suggest that this has gotten a lot more serious."

News of the 11 GOP senators' decision to cross party lines and vote on the measure proposed by Senate Minority Leader Chuck Schumer (D-NY) came after a number of House bills to partially or fully reopen the government attracted Republicans to defect -- in spite of urgings from their party and the White House.

Watch below: