The Arabian candidate wouldn't openly help terrorists. Instead, he would serve their cause while pretending to be their enemy.
After an attack, he would strike back at the terrorist base, a necessary action to preserve his image of toughness, but botch the follow-up, allowing the terrorist leaders to escape. Once the public's attention shifted, he would systematically squander the military victory: committing too few soldiers, reneging on promises of economic aid. Soon, warlords would once again rule most of the country, the heroin trade would be booming, and terrorist allies would make a comeback.
Meanwhile, he would lead America into a war against a country that posed no imminent threat. He would insinuate, without saying anything literally false, that it was somehow responsible for the terrorist attack. This unnecessary war would alienate our allies and tie down a large part of our military. At the same time, the Arabian candidate would neglect the pursuit of those who attacked us, and do nothing about regimes that really shelter anti-American terrorists and really are building nuclear weapons.
Again, he would take care to squander a military victory. The Arabian candidate and his co-conspirators would block all planning for the war's aftermath; they would arrange for our army to allow looters to destroy much of the country's infrastructure. Then they would disband the defeated regime's army, turning hundreds of thousands of trained soldiers into disgruntled potential insurgents.
After this it would be easy to sabotage the occupied country's reconstruction, simply by failing to spend aid funds or rein in cronyism and corruption. Power outages, overflowing sewage and unemployment would swell the ranks of our enemies.
Who knows? The Arabian candidate might even be able to deprive America of the moral high ground, no mean trick when our enemies are mass murderers, by creating a climate in which U.S. guards torture, humiliate and starve prisoners, most of them innocent or guilty of only petty crimes.
At home, the Arabian candidate would leave the nation vulnerable, doing almost nothing to secure ports, chemical plants and other potential targets. He would stonewall investigations into why the initial terrorist attack succeeded. And by repeatedly issuing vague terror warnings obviously timed to drown out unfavorable political news, his officials would ensure public indifference if and when a real threat is announced.
Last but not least, by blatantly exploiting the terrorist threat for personal political gain, he would undermine the nation's unity in the face of its enemies, sowing suspicion about the government's motives.
