Stock markets across Europe opened tentatively on Tuesday morning as the world gears up for the presidential elections across the Pond later today. While all eyes will likely be on the US today, investors had plenty to distract them this morning in London, with a barrage of trading updates and results from a number of heavyweight stocks to digest, including M&S, G4S, Babcock and InterContinental Hotels.The latest polls suggest that incumbent President Barack Obama holds a narrow lead over Republican challenger Mitt Romney but the final result could still go either way."Even if Barack Obama manages to hold on to his presidency without a majority in the Senate and Congress it will be hard to pass any new laws without having to compromise with the Republican party, making major reforms rather unlikely  which in turn might continue to hamper the economy and job growth," said Markus Huber, the head of German HNW trading at ETX Capital. "It might be the case that overall it matters less who will be elected as president of the US tonight instead the question will be, will the new president have the support and power to turn the economy around and bring down high unemployment or will we have a similar situation as we had in the past two years when Republican retook Congress in 2010  making it very difficult for President Obama to pass new laws."FTSE 100: ARM and M&S gain early onChip designer ARM jumped after saying that it is leading a consortium which is to acquire the patent portfolio of MIPS Technologies, the US semiconductor design company, in order to reduce the risk of expensive patent infringement suits in the chip design industry.High Street bellwether Marks & Spencer rose this morning after announcing that second-quarter revenue gained 2.5%, driven by a strong performance from food sales and a handy contribution from the group's international stores.Primark and foods group Associated British Foods was wanted after profits and revenues edged higher in the year to September 15th. Holiday Inns and Crowne Plaza hotels owner InterContinental Hotels Group advanced after seeing revenue per available room (RevPAR) grow across all regions in the third quarter.Property group Capital Shopping Centres rose after outperforming the market as the number of shoppers visiting its shopping centres rose for the second quarter in a row.Security group G4S was higher after saying its financial position continues to be strong and it "remains on track to meet its cash conversion target of 85% of PBITA [profit before interest, tax and amortisation] for the full year."Water and waste group Pennon edged higher after signing a 25-year South London Waste Treatment Services Public Private Partnership (PPP) contract for the London Boroughs of Croydon, Kingston, Merton and Sutton.Heading the other way was engineering support services group Babcock despite in-line earnings in the first half and a robust increase in its order book.Oilfield services group Petrofac failed to please investors with the announcement of a "strategic alliance" with AIM-listed Bowleven to develop the latter's Etinde Permit, offshore Cameroon, which will see Petrofac invest up to $500m.FTSE 100 - RisersARM Holdings (ARM) 721.00p +3.74%Resolution Ltd. (RSL) 227.80p +2.98%G4S (GFS) 267.90p +2.72%Marks & Spencer Group (MKS) 395.00p +1.83%InterContinental Hotels Group (IHG) 1,549.00p +1.64%Lloyds Banking Group (LLOY) 43.45p +1.41%Kingfisher (KGF) 290.40p +1.18%Capital Shopping Centres Group (CSCG) 339.30p +0.86%Aviva (AV.) 336.30p +0.81%ITV (ITV) 88.05p +0.80%FTSE 100 - FallersBabcock International Group (BAB) 950.50p -3.89%Admiral Group (ADM) 1,052.00p -1.41%Standard Chartered (STAN) 1,463.50p -1.31%Weir Group (WEIR) 1,811.00p -1.09%AstraZeneca (AZN) 2,880.50p -0.40%GKN (GKN) 212.70p -0.37%British American Tobacco (BATS) 3,119.00p -0.29%Bunzl (BNZL) 1,018.00p -0.29%Tate & Lyle (TATE) 736.00p -0.27%Pearson (PSON) 1,237.00p -0.24%FTSE 250 - RisersJD Sports Fashion (JD.) 772.00p +3.49%Ruspetro (RPO) 106.00p +2.91%Ted Baker (TED) 995.00p +2.26%Redrow (RDW) 165.20p +2.23%Kier Group (KIE) 1,290.00p +1.90%Daejan Holdings (DJAN) 2,900.00p +1.72%TalkTalk Telecom Group (TALK) 193.30p +1.68%Phoenix Group Holdings (DI) (PHNX) 495.50p +1.54%Imagination Technologies Group (IMG) 471.50p +1.40%Hansteen Holdings (HSTN) 76.85p +1.39%FTSE 250 - FallersTalvivaara Mining Company (TALV) 124.80p -3.78%Genus (GNS) 1,449.00p -1.83%African Barrick Gold (ABG) 420.80p -1.41%St. Modwen Properties (SMP) 206.00p -1.39%Kenmare Resources (KMR) 38.58p -1.38%Menzies(John) (MNZS) 599.00p -1.24%BTG (BTG) 331.90p -1.10%Yule Catto & Co (YULC) 146.80p -1.08%Hochschild Mining (HOC) 486.10p -1.04%Lonmin (LMI) 494.30p -1.04%BC