It was certainly used as justification for the emergency decree 'For the Protection of People and State', which was passed in a cabinet session on the morning after the fire. It had initially been proposed as a means of preventing arson in Prussia, but was later extended to the entire Reich. Amongst its provisions, it allowed the police to arrest and indefinitely detain anyone suspected of treason, arson or incitement to riot. Despite Hitler avowing that 'the normal order of things would return' after the Communist threat had been overcome, the decree was used against Nazi opponents to decisive effect. Given that the Communist KPD was amongst the main obstacles to any electoral gains for the NSDAP, the fire was a significant pretext for the rounding-up and torture of left-wing politicians, intellectuals and trade unionists, 4000 in all. Hitler and Goring were spurred into action, acting on the premise of a suspected Communist uprising (the fire being the first act of sabotage). So in short, the fire was the catalyst for a restructuring of the political climate, making it more difficult for a left-wing opposition - its press silenced and leaders detained - to succeed.

Whether or not this had a greater impact on the Nazis' electoral success than, say, the political implications of the Wall St. Crash and ensuing depression in Germany, is still a matter of perspective. It is clear that the March election 'victory' (a 44% share of the vote) was in some way facilitated by a 'late surge' towards Nazism following the fire, and the decree itself proved popular as a means of ensuring Germany's protection from Communism. But one could make the case that the election could have been a greater success for the Nazis and that the left-wing and centre parties held firm. This is arguably irrelevant, insofar as the Nazis saw the election as a resounding victory, on which a revolution had been built. It gave impetus to their campaign to 'restore order', targeting their opponents and seeking allegiance with renewed zeal,

So to conclude, the fire was the precursor to a violent repression of the Left, falsely implicated in arson/incitement to start a 'revolution'. It contributed to a significant (albeit overstated) victory for the NSDAP and, most importantly of all, was the first 'instrument of power' for a new dictatorship.

Sources: Kershaw, I., Hitler (one volume ed.) Craig, G. I., Germany 1866-1945